This invention relates generally to an electrostatographic printer or copier, and more particularly concerns a flexible belt cleaning apparatus used therein.
In an electrophotographic application such as xerography, a charge retentive surface (i.e., photoconductor, photoreceptor or imaging surface) is electrostatically charged and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. This process is well known, and useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charged surface may be image-wise discharged in a variety of ways. Ion projection devices where a charge is image-wise deposited on a charge retentive substrate operate similarly.
Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed on automatic xerographic devices utilizes a brush with soft conductive fiber bristles or with insulative soft bristles which have suitable triboelectric characteristics. While the bristles are soft for the insulative brush, they provide sufficient mechanical force to dislodge residual toner particles from the charge retentive surface. In the case of the conductive brush, the brush is usually electrically biased to provide an electrostatic force for toner detachment from the charge retentive surface. The fixed radius of commonly used brushes can limit cleaning applications. Toner particles adhere to the fibers (i.e. bristles) of the brush after the charge retentive surface has been cleaned. The process of removing toner from these types of cleaner brushes can be accomplished in a variety of ways. Typically, brush cleaners use flicker bars to provide the detoning function which may not sufficiently clean the particles from the brush fibers.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,320,774 to Rogers discloses a mechanical toothbrush with a brush drive unit coupled to a rotating device such as an electric motor. The brush drive unit alternately rotates a first belt brush in a first direction while maintaining a second belt brush in a substantially fixed position and rotates the second belt brush in a second direction while maintaining the first belt brush in a substantially fixed position.
U.S. Pat. No. 4,457,615 to Seanor discloses a belt brush constructed of alternate conductive and non-conductive segments which causes one conductive segment which is being used for charging to be electrically isolated from another conductive segment which is being used for cleaning. Different voltages can be simultaneously applied to each of the segments without adversely affecting the operation of the other. A single detoning roller is provided to remove toner particles from the brush.
U.S. Pat. No. 5,381,218 to Lundy discloses a conductive flexible cleaner brush belt having a plurality of detoning stations to remove particles from the brush fibers. At least one of the rollers about which the flexible belt brush is mounted has a small diameter for spreading the brush fibers apart. The spreading of the fibers creates a node affect as the fibers rebound, with adjacent fibers opening to create a moving node affect. An air vacuum removes the particles from the brush fibers.